The invention relates to a method, a device system and a computer program element for transmitting print data. It particularly relates to high-performance print systems, wherein print data, with speeds of more than 40 pages up to a few thousand pages per minute, are transmitted by a host computer or spooler to a print device.
For example, such a print system is described in the publication “Das Druckerbuch, Dr. Gerd Goldmann (publisher), Oce Printing Systems GmbH, publication 4a, Poing (May 1994), ISBN 3-00-00 1019-X” in chapter 10, particularly under the headline “Blockschaltung Hardware” with the title “SRA Controller”, pages 10-4 through 10-5.
Efficient connecting lines (channels) supporting a command structure are used in such systems for transmitting data. For example, such channels are the system/360 or the system/370, which have been specified by the company International Business Machines Corporation (IBM). These channels are described in greater detail in the IBM publications “Enterprise System Architecture/390, System/360 and System 370/I-O Interface Channel to Control Unit, No. GA-22-6974-10, 11. Publication, September 1992” and “Enterprise Systems Architecture/390, Common I-O Device,No. SA-7204-01, 2nd publication, April 1992”.
The print data themselves can be transmitted in different print languages such as AFP (Advanced Function Presentation), PCL (Printer Command Language) or IPDS (Intelligent Printer Data Stream).
The what is referred to as ESCON interface, which is described in the IBM publication No. FA 22-7202 with the title “IBM Enterprise Systems Architecture/390 ESCON I/O Interface”, also supports such a command structure.
The aforementioned publications are incorporated into the present specification by reference.
A basic property of such command structures is that the data stream transmitted by the channel or the data interface is divided into channel command words—what are referred to as CCW's (Channel Command Words). It is differentiated between different command types, for example what are referred to as control commands carrying out specific device control functions such as the positioning of a hard disk mechanism in a fixed-disk storage. What is referred to as a read-command starts a transmission of data from the reception unit to the transmission unit. For example, the status of the printer controller can be transmitted to the host computer by a read-command word when data are transmitted from a host computer to a controller of a printer. The connection of the data interface to a printer controller also is called a channel-specific interface (CSI).
Another basic property of the cited interfaces is that a specific unit, in a data transmission system, always is fixed as the what is referred to as transmitter (referred to as channel in many cases) and that the unit connected to the transmission unit is fixed as a reception unit (referred to as an I-O device in many cases). For example, in a printing system wherein a print device is connected to a host computer or to a spooling unit, the host computer or spooler normally is the transmission unit (channel), whereas the print device contains the reception unit (I/O-device). This classification is explained in that the print data are transmitted regularly from the host computer to the print system, i.e., the data flow predominately occurs from the host computer to the print device, whereas only a few bits of status information are to be transmitted from the print device to the host computer.
In the communication between a host computer and a print device, the write-CCW's therefore represent the dominating quantity regarding channel command words, since the print data are transmitted by these commands.
The data line between the host computer and the print device increasingly represents a bottleneck with respect to the print performance.